title: Variability in absolute apparent diffusion coefficient values across different platforms may be substantial: a multivendor, multi-institutional comparison study.
abstract: OBJECTIVE
  To determine whether and to what degree absolute apparent diffusion coefficient (ADC) values vary between different imagers, vendors, field strengths, and intraimager conditions.
  
  
  METHODS
  Informed consent and institutional review board approval were obtained. Diffusion-weighted (DW) images with nearly identical parameters were obtained at 1.5 and 3.0 T from 12 healthy volunteers at seven institutions by using 10 magnetic resonance (MR) imagers provided by four different vendors. ADC maps were generated from isotropic DW maps, and images with a b value of 0 sec/mm(2) were generated by using in-house software. The mean pixel values for the brain tissues were calculated for evaluating the differences among coil systems, imagers, vendors, and magnetic field strengths.
  
  
  RESULTS
  The absolute ADC values of gray and white matter from the same vendor varied substantially: 4%-9% at 1.5 and 3.0 T. With the exception of one vendor, the intervendor variability at 1.5 T was as high as 7%. Moreover, there was substantial intraimager variability, up to 8%, depending on the coil systems in certain imagers.
  
  
  CONCLUSIONS
  There is significant variability in ADC values depending on the coil systems, imagers, vendors, and field strengths used for MR imaging. The relative ADC values may be more suitable than absolute ADC values for evaluating diffusion abnormalities in patients enrolled in multicenter acute ischemic stroke trials.
authors.affiliation: Advanced Medical Research Center, Iwate Medical University, 19-1 Uchimaru, Morioka 020-8505, Japan. masasaki@iwate-med.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Sasaki
authors.forename: Kei
authors.initials: K
authors.lastname: Yamada
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Mieko
authors.initials: M
authors.lastname: Matsui
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ida
authors.forename: Shunrou
authors.initials: S
authors.lastname: Fujiwara
authors.forename: Eri
authors.initials: E
authors.lastname: Shibata
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000295:instrumentation*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D011446:Prospective Studies